Sarcoids - major concern or just unsightly?

Sarcoids, whilst not life threatening in themselves, can directly lead to a horse being euthanased. They are also a common cause of horses failing a pre-purchase vetting. Clearly a sarcoid, which could initially be dismissed as an insignificant wart, needs to be taken seriously. It is important to recognise the condition and be aware of the possible consequences.

What are sarcoids?

Sarcoid by eye of horseSarcoids are a type of tumour which affect the skin and/or the tissue just below the skin. Their growth may be fast or slow and is often irregular. The good news is that they do not spread to the internal organs.

Any equine (including donkeys and zebra) of any age, sex or colour can be affected. There does appear to be some genetic component as some Arab lines seem susceptible while Lipizzaners are more resistant. Although sarcoids occur worldwide there are regional variations in the number of lesions per horse and the most common position on the body. In the UK, horses typically develop 20 - 30 lesions (2 - 5 is the average in many countries) although an individual horse can develop hundreds. They are located most often near the eyes, ears, mouth, axilla (armpit) and groin. It is not coincidence that these are areas where flies feed.

Sarcoids can start to appear at any age but they are usually first noticed on a horse between the ages of 2 and 10. A horse with one sarcoid is likely to develop more.

The cause is not clear but there is a strong association with the bovine papilloma virus. It does not appear to be transmitted from horse to horse by direct contact but there are indications that it can be transmitted via tack and grooming equipment so it is advisable to keep separate equipment for a horse with sarcoids.

Why are sarcoids a concern?

Sarcoid by ear of horseApart from being unsightly, the surface of the sarcoid is prone to cracking and bleeding, particularly if rubbed by tack. This can result in infection and flies may lay eggs in large sarcoids so that maggots develop. Irritation by flies also makes the horse more likely to rub which worsens the situation.

Damage to a sarcoid can cause it to become aggressive and develop rapidly - sometimes into a huge mass of tissue. Sarcoids are also likely to develop in an open wound so, if a horse has even a small sarcoid, any open wound is a concern. It is important to distinguish between a wound with proud flesh (which may develop as a natural part of the healing process) and a sarcoid, as the treatment is completely different for each. If the wound is near a joint then the developing sarcoid could restrict the horse's movement.

A horse with sarcoids can be difficult to sell and, as a horse with even one sarcoid is likely to develop more, it is a valid concern for potential purchasers. The main concerns are:

  1. treatment can be expensive and is not always effective
  2. sarcoids may develop in tack areas or near joints making the horse unfit for purpose
  3. open wounds may require additional veterinary treatment
  4. potential problems obtaining insurance
  5. difficulty of resale
  6. cosmetic

If sarcoids make the horse unfit for riding and difficult to sell on, then the horse is likely to be euthanased.

Recognising sarcoids

Sarcoids can be confused with other skin conditions and, although a vet can normally identify them, a biopsy is the only certain way to diagnose them. Be warned, however, that taking the biopsy could disturb the sarcoid and cause it to become more aggressive.

There are several types which have a different appearance

  1. occult: a grey, scaly, circular patch - looking somewhat similar to ringworm
  2. verrucous: similar to the occult type but more irregular in shape and extending deeper into the skin
  3. nodular: round nodules, mostly under the skin
  4. fibroblastic: usually large, rapidly growing, ulcerated areas (cauliflower like) which can be on a stalk - they often develop from other types of sarcoid (especially if they are damaged) or at a wound site
  5. mixed - a combination of the above types
  6. malignant - very aggressive, spreading rapidly in size and area, usually look like ulcerated nodules. Fortunately this form is rare, although it seems more common in the UK than in other countries.

Sarcoids tend to increase in size during the winter and multiply over the summer so fly control is important.

Treatment

There is no single treatment which is effective in all cases and more than 40 types of treatment are available. As with any tumour, the sooner a sarcoid is treated the better the prognosis - especially if the horse is less than 4 years old. If the treatment fails, sarcoids can become more aggressive and increase in number. It is therefore extremely important to get veterinary advice as soon as possible and DO NOT ATTEMPT TREATMENT YOURSELF.

The most common types of treatment are:

  1. benign neglect - a vet may advise no immediate action for small, slow growing sarcoids and to monitor their progress. The vet should be called if there is any sudden change.
  2. topical (i.e. applied to the skin) ointment - only use ointment recommended by your vet as some contain ingredients (e.g. Aloe Vera) which stimulate cells and could therefore cause a sarcoid to become more aggressive.
  3. strangulation - tying a strangulating band around the base of a small nodular sarcoid can be an effective method of killing it over a number of weeks - provided it has no root structure. Owners sometimes attempt this method themselves but if the sarcoid has roots then it will make the situation significantly worse.
  4. BCG injection - using the human TB vaccine can be effective on lesions near the eyes but less effective elsewhere, and on the legs can be detrimental
  5. cryotherapy - freezing the sarcoid off, only effective for sarcoids of limited size and depth. There is a high rate of reoccurrence and can cause a lot of scarring
  6. surgical removal - can be used for small sarcoids in safe areas but is not always successful
  7. radiation - this is usually very effective but is very expensive and not commonly available

Case study

Sarcoid by mouth of horseThe pictures show a 5 year old horse starting to develop sarcoids. Those shown are near the eye, ear and mouth, another larger one had developed on the chest. Although small, the main concern was that they were developing close to the bit and browband. The vet gave several treatment options - the sarcoid on the chest was large enough to apply a strangulating ligature, the others could be monitored and if they grew much bigger could be treated with a BCG injection. However as they were all quite small she suggested trying a non-prescription ointment which she knew had been sccessful in some cases. This was the option taken and although for a couple of months there seemed to be no change, the sarcoids started to flake off until they were gone completely. The horse is now 12 and has never developed another sarcoid.

It was fortunate that this case resolved so easily but probably shows the benefit of early veterinary advice and treatment.

The future

There is research going on in many countries to find new treatment options for sarcoids. Among the most promising are using a mistletoe extract, acyclovir (a drug used to treat humans for chickenpox), gene silencing technology and electrochemotherapy (a combination of chemotherapy and electrical field pulses).

Unfortunately a universal cure still seems a long way off. In the meantime careful monitoring of the horse and obtaining early veterinary advice is the best action that can be taken by owners.

More information

Posted on 14 September, 2011

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